BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										$ 4,303		$ 4,073		$ 4,253
Realized investment gains (losses), non-operating	[1]									(208)		55		171
Other non-operating income (loss)										(28)	[2]	(266)	[2],[3]	67
Earnings before income taxes		$ 1,153	$ 963	$ 834	$ 1,117	$ 1,110	$ 864	$ 874	$ 1,013	4,067		3,862		4,491
Income taxes applicable to pretax operating earnings										1,491		1,403		1,456
Effect of foreign currency translation on operating earnings										141		(198)		(117)
Gain (loss) on change in fair value of derivative, interest rate component, operating										85		85		44
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										3,334		3,175		3,458
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										1,208		1,101		1,073
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										18		14		(2)
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										4,560		4,290		4,529
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										(128)		(146)		(198)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings										(129)		(71)		$ (78)
Senior Notes due 2039 and 2040
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Expense on extinguishment of debt										$ 137
8.50% senior notes due May 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Expense on extinguishment of debt												230
Twenty Fifteen Profit Repatriation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Foreign currency transaction gain (loss), realized												$ (20)

[1] Excluding a gain of $85 in both 2016 and 2015 and $44 in 2014 related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is classified as an operating gain when analyzing segment operations

[2] Includes expense of $137 in 2016 and $230 in 2015 for the payments associated with the early extinguishment of debt

[3] Includes a loss of $20 related to the change in value of yen repatriation received in advance of settlement of certain foreign currency derivatives. This loss was offset by derivative gains included in realized investment gains (losses).